Articles and notes on Java, Kotlin, Android, Spring, AI and LLM engineering.https://romankryvolapov.com/enhttps://romankryvolapov.com/en/android-components-and-views/https://romankryvolapov.com/en/android-components-and-views/Android internals for interviews: Activity, Fragment and Service lifecycles, Context, Intent, WorkManager, RecyclerView and MVP vs MVVM vs MVI.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/android-paging-3/https://romankryvolapov.com/en/android-paging-3/Building pagination in Android with Paging 3: PagingSource, PagingDataAdapter, load-state footers, and wiring it into AdapterDelegates.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/android-push-provisioning-api/https://romankryvolapov.com/en/android-push-provisioning-api/Adding bank cards to Google Pay from an Android app: tapAndPay SDK setup, API allowlisting, Google Pay UI rules, and encrypted OPC handling.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/cursor-ide-best-practices/https://romankryvolapov.com/en/cursor-ide-best-practices/Practical Cursor IDE habits: project and folder Rules, the Auto model, MCP servers, breaking tasks into steps, and reviewing every diff before commit.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/recyclerview-adapterdelegates/https://romankryvolapov.com/en/recyclerview-adapterdelegates/Building dynamic Android UI with RecyclerView and AdapterDelegates: writing delegates, reusing list items, and diffing them without DiffUtil boilerplate.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/google-guava-in-examples/https://romankryvolapov.com/en/google-guava-in-examples/A tour of Google Guava through Kotlin examples: Multimap, BiMap, Table, caching, string utilities, hashing, IO helpers and concurrency.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/grpc/https://romankryvolapov.com/en/grpc/How gRPC works on top of HTTP/2 and Protocol Buffers, where it beats REST for internal services, and how to build a Kotlin server and client.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/ktor-manual/https://romankryvolapov.com/en/ktor-manual/Building a Kotlin server with Ktor: Exposed and JDBI for the database, Koin for dependency injection, Mockk and Testcontainers tests, Flyway migrations.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/project-loom-manual/https://romankryvolapov.com/en/project-loom-manual/Project Loom virtual threads in Java: how the JVM schedules them on carrier threads, how they differ from Kotlin Coroutines, and enabling them in Spring.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-kotlin-multithreading/https://romankryvolapov.com/en/java-kotlin-multithreading/Java and Kotlin concurrency explained: volatile, synchronized, ReentrantLock, coroutines and Channels, RxJava operators and backpressure strategies.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-kotlin-theory/https://romankryvolapov.com/en/java-kotlin-theory/Big-O costs of collection operations, design patterns, SOLID, inheritance versus composition and higher-order functions in Java and Kotlin.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-core-questions/https://romankryvolapov.com/en/java-core-questions/Java Core interview answers: data types, collections and HashMap, generics, reflection, JVM memory layout and how the garbage collector works.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-spring-cloud/https://romankryvolapov.com/en/java-spring-cloud/Cloud services for Java across AWS, Google Cloud and Azure: side-by-side equivalents, cost optimization, serverless, Git LFS and submodules.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-spring-concepts/https://romankryvolapov.com/en/java-spring-concepts/Core backend concepts behind Spring: Saga and Rollback, SOLID, Clean Architecture, REST vs RPC vs GraphQL, IoC and DI, Spring MVC and Project Reactor.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-spring-data-storage/https://romankryvolapov.com/en/java-spring-data-storage/Data storage in Spring: ACID and isolation levels, @Transactional, JPA vs JDBC, Spring Data repositories, Redis caching, Flyway and indexes.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-spring-questions/https://romankryvolapov.com/en/java-spring-questions/A navigable index of Java developer interview questions: Java Core, Kotlin, concurrency, Spring annotations and components, microservices, and SQL.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-spring-microservices/https://romankryvolapov.com/en/java-spring-microservices/Microservice communication in Spring: REST and WebClient, Kafka and RabbitMQ, Docker and Kubernetes, Eureka, Cloud Gateway, and request tracing.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-spring-annotations/https://romankryvolapov.com/en/java-spring-annotations/A reference to Spring annotations with Kotlin examples: @Component, @Bean, @Transactional, request mapping, JPA, and how @Component differs from @Bean.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/java-spring-components/https://romankryvolapov.com/en/java-spring-components/Configuring application.properties, WebSocket, GraphQL, OAuth 2.0, Spring Security, Actuator, WebFlux and Batch with real code and config examples.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/kotlin-2-key-syntax-changes/https://romankryvolapov.com/en/kotlin-2-key-syntax-changes/What changed in Kotlin 2.0 syntax: context receivers, value classes, sealed interfaces, destructuring in for loops and pattern matching in when.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/kotlin-core-questions/https://romankryvolapov.com/en/kotlin-core-questions/How coroutines and suspend actually work, when to use launch instead of async, plus scope functions, delegates, extensions and companion objects.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/kubernetes/https://romankryvolapov.com/en/kubernetes/How Kubernetes works: control plane architecture, namespaces, load balancing, everyday kubectl commands, the Dashboard and Prometheus monitoring.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/llama-cpp/https://romankryvolapov.com/en/llama-cpp/How inference works inside llama.cpp: loading a GGUF model, tokenization, building the compute graph, the KV cache, and token sampling.Wed, 04 Feb 2026 00:00:00 GMThttps://romankryvolapov.com/en/android-logging-to-file/https://romankryvolapov.com/en/android-logging-to-file/A LogUtil logger for Android that writes debug and error logs plus OkHttp network traffic into separate txt files on the device storage.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/lora-fine-tuning/https://romankryvolapov.com/en/lora-fine-tuning/Fine-tuning an LLM with LoRA: when it beats RAG, how to train adapters for gemma-3-4b with unsloth and peft, and export the result to GGUF.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/microservices-security/https://romankryvolapov.com/en/microservices-security/Auth microservices, API Gateway, mTLS and certificates: how to store passwords safely, stop brute-force attacks and choose encryption algorithms.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/android-mock-interceptor/https://romankryvolapov.com/en/android-mock-interceptor/Mocking server responses in Android with a custom OkHttp Interceptor: a MockResponse model, a URL-keyed map, and wiring it into OkHttpClient.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/neural-networks-basics/https://romankryvolapov.com/en/neural-networks-basics/How an LLM actually works: tokenization, embeddings, transformer attention, quantization, and the samplers that pick each next token.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/offline-ai-launcher/https://romankryvolapov.com/en/offline-ai-launcher/Offline AI Launcher runs LLMs like Gemma, DeepSeek, Llama and Qwen straight on your Android phone from .gguf files, with no internet or subscription.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/prompt-engineering/https://romankryvolapov.com/en/prompt-engineering/Delimiters, XML tags, few-shot examples, pseudocode and rule hierarchy — how to format prompts for ChatGPT, Claude or Gemini and get predictable output.Fri, 20 Feb 2026 00:00:00 GMThttps://romankryvolapov.com/en/rag-and-function-calling/https://romankryvolapov.com/en/rag-and-function-calling/RAG, function calling and CAG for local LLMs: how vector search works, with working examples in Kotlin, Dspy, LangChain, LangChain4j and llama.cpp.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/relational-sql-databases/https://romankryvolapov.com/en/relational-sql-databases/SQL syntax, views and indexes, JOIN and CTE queries, pessimistic and optimistic locking, and reading query plans in PostgreSQL, MySQL and Oracle.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/intellij-idea-launch-options/https://romankryvolapov.com/en/intellij-idea-launch-options/What each flag in Edit Custom VM Options actually does: heap sizes, Garbage Collector choice, code cache, and memory tuning for Android Studio.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/mapstruct-manual/https://romankryvolapov.com/en/mapstruct-manual/Practical MapStruct recipes for Kotlin: mapping mismatched field names, @Named methods, reusing mapping logic, and avoiding common compile-time errors.Wed, 21 Jan 2026 00:00:00 GMThttps://romankryvolapov.com/en/vector-databases/https://romankryvolapov.com/en/vector-databases/How vector databases work: embeddings, HNSW indexing and similarity search, plus a comparison of Milvus, Qdrant and Weaviate with Milvus code.Wed, 21 Jan 2026 00:00:00 GMT